Roland MKS20 sounds like Phaser

I have a Roland MKS20 that I’m having a small issue with. I’ve had the unit for 10+ years. I had it maintenance recently. Now when the chorus and tremolo are engaged, the unit sounds like it’s running through a phaser effect or pedal (hopefully that makes sense). It’s never down that until after it was maintenance. Any idea what that could be and how I can fix it? Thanks